CODEWITHSUNDEEP
mongodbmeteor
blueren
blueren

Reputation: 2860

MongoDB and one-to-many relation

I am trying to come up with a rough design for an application we're working on. What I'd like to know is, if there is a way to directly map a one to many relation in mongo.

My schema is like this:

I was going through MongoDB documentation wherein they mention things relating to Embedded document vs. multiple collections. By no means am I having a detailed clarity over this as I've just started with Mongo and meteor.

Question is, what could seemingly be a better approach? Having multiple small collections or having one big embedded collection. I know this question is somewhat subjective, I just need some clarity from folks who have more expertise in this field.

Another question is, suppose I go with the embedded model, is there a way to update only a part of the document (specific to the interface alone) so that as and when itf is added, it can be inserted into the same device document?

Upvotes: 0

Views: 441

Answers (1)

Felipe Sulser
Felipe Sulser

Reputation: 1195

It depends on the purpose of the application.

Big document

A good example on where you'd want a big embedded collection would be if you are not going to modify (normally) the data but you're going to query them a lot. In my application I use this for storing pre-processed trips with all the information. Therefore when someone wants to consult this trip, all the information is located in a single document. However if your query is based on a value that is embedded in a trip, inside a list this would be very slow. If that's the case I'd recommend creating another collection with a relation between both collections. Also for updating part of a document it would be slow since it would require you to fetch the whole document and then update it.

Small documents with relations

If you plan on modify the data a lot, I'd recommend you to stick to a reference to another collection. With small documents, this will allow you to update any collection quicker. If you want to model a unique relation you may consider using a unique index in mongo. This can be done using: db.members.createIndex( { "user_id": 1 }, { unique: true } ).

Therefore:

  • Big object: Great for querying data but slow for complex queries.
  • Small related collections: Great for updating but requires several queries on distinct collections.

Upvotes: 2

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